When I talk to my patients with lymphedema, I often need to tell them about their lymphatic system. Beyond knowing of lymph nodes or glands in their neck, most don't recall having heard anything about it. Surprisingly, today's medical students often have less than 1 hour on the lymphatic system education in medical school. In physical therapy school (35 years ago), instruction was woefully inadequate. Today, more is known - and most therapy schools do spend significant time on the lymphatic system and lymphedema. For those who missed it, here is the lymphatic system in a nutshell.

The Lymphatic System: An Overview

The lymphatic system includes the thoracic duct (main vessel), which receives the lymph fluid from smaller vessels called lymph collectors. The latter receive lymph fluid from the initial lymphatic vessels. These small vessels form a fine 3D mesh near the venous and arterial capillaries from the head to toes and fingers. The lymph nodes are bean shaped tissues grouped at the knees, hips, elbows, shoulders, abdomen, spine, between the ribs, and at the neck.

The lymph fluid is composed of the fluid in the "third space" of the body—not in an organ and not in a vessel. This interstitial space is where nutrition and fluid goes from the blood capillaries to end organs, and back into venous capillaries. This takes place by diffusion due to osmosis, filtration, and active transport by the cell walls. The speed at which this happens is affected by concentration gradient, temperature, and distance.

The lymph fluid consists of intercellular fluid, larger molecules, protein, blood waste, possibly cancer cells, and immune products. The lymph fluid flows into the initial lymphatics or capillaries through swinging tips—microscopic gates that open from tension on filaments attached from the gate to adjacent structures. As the third space fills with fluid and solids, the filament is stretched and pulls open the gate, allowing lymph fluid to enter. Fluid dynamics, muscle pumps, and contractile lymph collectors move the lymph fluid toward the body core. Lymph nodes process the lymph fluid and are home base for the lymphocytes (B and T cells).

Antibodies are created when B-cell lymphocytes are exposed to antigens. The antigen is thus marked for destruction, carried out by T-cells. In this way, bacteria, viruses, cell waste, dead cells, and cancer cells are filtered from the body. Macrophages stored in the lymph node fight infection and multiply when activated to travel to infected areas. In the gut, lymphatic capillaries uptake fat and fat-soluble vitamins.

The Importance of Lymphatic Organs

There are several lymphatic organs: spleen, thymus, appendix, bone marrow, tonsils, etc. For treating patients with lymphedema, this is where the lymphocytes and macrophages are formed or stored. Filtering or storage of the blood to remove debris, old cells, foreign bodies, and recycling components of blood are important tasks here as well.

The fun starts when this complex system doesn't work and lymphedema therapists need to figure out how to best manipulate the patient's body into processing the lymph fluid. Visit my blog next month for the story.

Lymphedema can great impact the quality of life for patients living with this condition. Visit lymphedematreatmentact.org to motivate your senator as a co-sponsor for this important legislation - to ensure access to vitally needed compression garments for lymphedema patients.

Sources
www.cliffsnotes.com/study-guides/anatomy-and-physiology/the-lymphatic-s…
http://www.lymphnotes.com/article.php/id/151/
http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/APIINotes7%20Lymp…

About the Author
Janet Wolfson is a wound care and lymphedema educator with ILWTI, and Lymphedema and Wound Care Coordinator at Health South of Ocala with over 30 years of field experience.